Method of making a composite golf shaft for a golf club



D. L. 'GRIMES Oct. 8, 1957 METHOD OF MAKING A COMPOSITE GOLF SHAFT FOR A GOLF CLUB Original Filed Jan. 27, 1955 DHV/D 4. aw/M55 INVENTOR- ATTOP/YEVS United States Patent METHOD OF MAKING A COMPOSITE GOLF SHAFT FOR A GOLF CLUB David L. Grimes, San Diego, Calif, assiguor to Narmco porting Goods Company, Costa Mesa, Califl, a corporation of California Original application January 27, 1955, Serial No. 484,362. gigideg and this application March 5, 1956, Serial No.

1 Claim. (Cl. 154-83) This invention relates to an improved form of composite shaft and, more particularly, to an improved composite shaft for a golf club. This application is a division of application by this inventor, Serial No. 484,362, filed January 27, 1955, for a Composite Shaft.

Golf clubs have been made having either wooden shafts or steel shafts. The steel shafts have found favor because they provide both greater driving range and control. The wooden shafts, although not having the same range and control as the steel shafts, have what is termed by the golfers a better feel. There is less shock or kick to the hands of the golfer when using a wooden club. They are better to handle in cold weather, because the rate of heat transfer of the wood is nowhere near that of the steel golf club, and, further, they do not deteriorate from corrosion caused by perspiration or from other sources in the same manner as the steel clubs are affected. The ideal club would be one which combines the range and control of the steel shaft with the feel of the wooden shaft.

A golf shaft made of structural glass plastic material has many advantages. It has an excellent feel. The weight may be lighter according to the design selected. The rate of heat transfer of the material is low; therefore, the club is much Warmer to the touch in cold weather. Further, such a shaft is resistant to corrosion due to hand perspiration or salt corrosion due to the atmosphere. It can be made to have a pleasing appearance since there are many varieties of colors and textures possible in the plastic materials.

A shaft for a golf club requires not only rigidity in bending, but also rigidity in torsion. Although structural glass plastic materials today have very high direct strengths, such as tension and compression, when compared to their specific gravity, the modulus of elasticity and the modulus of rigidity are lower than conventional structural materials on a weight basis. This means that a golf shaft made of these materials which has the same outside dimensions that is, outside diameters-and taper ratio as the usual golf shaft would not be sufficiently stiff in bending and the head would twist too much on impact with the golf ball. When a golf shaft deflects considerably more than usual and the head twists, it means less range and considerably more criticalness on control when striking the ball.

When designing a tube, such as a golf shaft, it is recognized that the only two factors that control bending and torsion stiffness are the section modulusthat is, the cross-sectional shape of the tubeand the modulus of elasticity, or modulus of rigidity. Since it appeared extremely desirable to maintain the slimness of the shaft and the same taper, not much advantage can be gained by the mere addition of glass plastic material, since it would mean that the additional material would increase the wall thickness of the tube inwardin other words, maintaining the outside diameter by reducing the inside diameter. This is fruitless however, since although there is more material, the strength to weight efficiency is re- 2,809,144 Patented Oct. 8, 1957 ice duced due to approaching the neutral axis of the tube. It would therefore appear that at this time the design of a golf club shaft, using only the glass plastic material alone, is not feasible. In order to obtain the benefits of glass plastic materials and to overcome their weak nesses, a new approach to the design of a golf club shaft employing these materials must be made.

An object of this invention is the provision of a shaft for a golf club which has the desirable characteristics of both the steel and wooden shafts.

Another object of this invention is the provision of a novel, composite shaft suitable for use as a golf club.

Still another object of the invention is to provide a composite shaft for golf clubs wherein the weight may be varied as desired, while maintaining the control and range of the steel shaft with the feel of the wooden shaft.

Yet another object of the invention is to provide a composite shaft for golf clubs which maintains the slimness and taper of presently known golf clubs without reducing the strength to weight ratio of the shaft.

These and other objects of the invention are achieved in a composite shaft wherein a tapered, hollow metal core has bonded thereto and wrapped around it several layers of a glass plastic material. The composite shaft has a desired length. The core may extend entirely over this desired length, or the core may extend for only a portion of this length. When the latter is the case, the metal core is positioned near the end where the head of the golf club is attached. By varying the length of the metal core and the number of wraps of the plastic cloth material, the characteristics of the shaft, as well as its. weight, may be varied as desired. The method of fabrication of the composite shaft is such as to provide a plastic structural material combined with a metal core which operates as one composite material giving physical characteristics different and advantageous over the conventional golf shaft.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claim. The invention itself, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in connection with the accompanying drawings, in which:

Figure 1 shows the shaft in the process of manufacture;

Figure 2 is a section on line 2-2 of Figure 1;

Figure 3 shows a view of the finished shaft; and

Figure 4 is a section on line 44 of Figure 3.

Referring now to Figure 1, this embodiment of the invention includes an insert 10 which may be of metal, preferably a heat-treated hollow steel tube having deflection characteristics similar to those desired on the finished shaft. This insert is tapered in a desired manner. This insert may extend the length of the shaft. If a lighter weight club with more flexibility is desired, then the insert is made less than the length of the shaft and the difference up to the desired length is made up by a mandrel 12, which fits adjacent to the insert and continues the taper of the insert to the desired length. The metal insert should have a protective covering, anodized or plated thereon, of a satisfactory alloy to retard corrosion or rusting.

A plastic material 14, which may consist of a glass fabric material impregnated with a thermosetting nylon modified phenolic resin, is cut to the desired length, and to provide a desired taper, and has a width which is determined by the number of wraps or layers of the material to be wound upon the core. The glass fabric material is a commercially available product of the Owens-Corning Fiberglas Corporation and is known in the market today as Fiberglas. The impregnating thermosetting plastic material is the preferred type. Other such materials, such as phenol formaldehyde, may also be used if desired. The

method of impregnating the glass fabric material is well known and will not be described here.

The metal shaft and mandrel are cleaned to remove any possible contaminants. A final cleaning of the metal is made with a material such as methyl ethyl ketone to remove any traces of lubricants, fingerprints, etc. The metal shaft is then coated with a structural metal adhesive. This is a material for bonding plastics to metal. Several types are commercially available, one of which is known as Metlbond which is a nylon modified phenolic material. The coating is then dried. This drying process may consist of an air and oven dry. The mandrel is coated with a suitable parting agent, such as waxes or silicone greases or others well known in the art, which will permit the removal of the mandrel from the composite shaft later. This material serves as a parting agent due to its waxy, nonadhesive nature. The glass fabric cloth then has one end tacked to an edge of the insert, or insert and mandrel, as may be seen from Figure 2. By tacking here is meant that a hot iron is used to press the glass cloth against the core. As previously stated, the glass fabric material is impregnated with a thermosetting phenolic resin, which preferably is at the stage where it is tacky, or practically dry, to enable the tacking. Glass fabric material in this state is known as B-stage plastic material.

The glass plastic material is then wrapped tightly around the core. A wrapping machine may be employed for this process, if desired. Then cellophane tape (not shown) is wrapped around the composite shaft in the form of a spiral. The cellophane serves to exert a pressure squeezing the plastic materials onto the metal insert when heated during the curing cycle. The composite shaft is then placed in an oven for curing. It was found that this curing process required for the materials employed approximately 330 over the period of one hour. The composite shaft is then removed from the oven and the cellophane is removed from the cured shaft. If the shaft has a mandrel, the mandrel can then be removed therefrom. The composite shaft may then be lightly sanded and an additional finish applied if desired. The finished product will then look like the composite shaft 16 shown in Figures 3 and 4.

The composite shaft is one wherein the plastic material provides the feel obtainable with wooden shafts, with the range and control of the steel shafts. Furthermore, by varying the number of wraps of plastic as well as the size of the steel insert, variations in club characteristics may be obtained. These variations are so simply obtained that this invention makes available tailoring of clubs to suit individual tastes.

The shape of the shaft need not necessarily be round as shown but may be given any type of streamlining desired to reduce Wind resistance. This can be simply achieved by either making the core have the desired shape or piling up the glass fabric in a desired manner.

Reinforcements may be added as desired to various points by additional arrangements of the glass plastic material being wrapped about the shaft at those points.

Accordingly, there has been shown and described a novel, useful, and economical method of manufacture for a composite shaft for golf clubs, as well as a novel golf club composite shaft.

I claim:

A method of fabricating a composite shaft for a golf club from a hollow metal insert which is less than the desired length of said shaft, and a thermosetting phenolic resin impregnated glass fabric cloth, said method comprising attaching a mandrel to said insert at one end to provide an over-all length equivalent to the desired length, cleaning said metal insert, coating said metal insert with a structural metal adhesive, drying said adhesive, coating said mandrel with a parting agent, tacking one end of said glass fabric cloth along an edge of said metal insert and said mandrel, wrapping layers of said cloth around said metal insert and said mandrel, wrapping cellophane around said cloth layers, heating until said thermosetting phenolic has set, removing said cellophane, and removing said mandrel.

References Cited in the file of this patent UNITED STATES PATENTS 1,317,146 Welles Sept. 23, 1919 2,054,769 Holtz Sept. 15, 1936 2,594,838 Alexander et al Apr. 29, 1952. 2,643,700 Havens June 30, 1953 

